Surprisingly Robust In-Hand Manipulation: An Empirical Study

We present in-hand manipulation skills on a dexterous; compliant; anthropomorphic hand. Even though these skills were derived in a simplistic manner; they exhibit surprising robustness to variations in shape; size; weight; and placement of the manipulated object. They are also very insensitive to variation of execution speeds; ranging from highly dynamic to quasi-static. The robustness of the skills leads to compositional properties that enable extended and robust manipulation programs. To explain the surprising robustness of the in-hand manipulation skills; we performed a detailed; empirical analysis of the skills' performance. From this analysis; we identify three principles for skill design: 1) Exploiting the hardware's innate ability to drive hard-to-model contact dynamics. 2) Taking actions to constrain these interactions; funneling the system into a narrow set of possibilities. 3) Composing such action sequences into complex manipulation programs. We believe that these principles constitute an important foundation for robust robotic in-hand manipulation; and possibly for manipulation in general.